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Hiwatt DR504 build

Discussion in 'Building the Classics' started by David Copeland, Jul 27, 2021.

  1. David Copeland

    David Copeland Member

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    Hello all,
    I have been working on a Hiwatt DR504 build for a couple of months now and I'm finished! I love the sound, I think it may be what I've been searching for for quite a while. I used a chassis/faceplates from Modulus and transformers from Classic Tone that I was able to find for sale still. As a result I'm using a 100 watt transformer/power supply design and a 50 watt OT designed to go in a Marshall 900. I have also combined about 3 or 4 of Dave Reeve's preamp designs utilizing the features that I liked best from each. Output power is around 60 watts rms at clipping and the bandwidth extends up to 20kHz for -3db. Anyway here's some shots:
    IMG_20210427_105707r1.jpg IMG_20210501_224748r1.jpg IMG_20210511_120132r1.jpg IMG_20210523_110630r1.jpg IMG_20210623_192449r1.jpg IMG_20210503_224633r1.jpg IMG_20210523_110811_1CSr1.jpg IMG_20210601_101948r1.jpg IMG_20210623_120103r1.jpg
     

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  2. william vogel

    william vogel Well-Known Member Gold Supporting Member

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    Very nice amp. Hiwatt is quite different than Marshall in tone and construction.
     
  3. David Copeland

    David Copeland Member

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    Yes it is. My big takeaway from this is that I will probably probably continue to use is the flax cord lacing on just about anything I do in the future. Once you get the hang of it, it's easy; and looks and handles so much better than zip ties for bundling wiring.
     
  4. _Steve

    _Steve Well-Known Member

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    Very nice! I recently built one too - I feel your pain and your joy :)

    Which phase inverter did you do?
     
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  5. David Copeland

    David Copeland Member

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    I used the early 70s phase inverter. The one with the 82k and 91k plate resistors. The input stage uses a single shared 1.5K cathode resistor bypassed with a 50uf cap. Cathode follower stage is feeding the tone stack and the PI. The tone stack is the more complicated one from the late 60s four input ver. I preamp. Probably the main deviation from DR's designs is using a buss ground system that ties to the chassis only at the input jacks; none of Dave's multiple grounds to chassis. Oh, and I used 1 watt resistors minimum dissipation through out. (They're also prettier.)
     
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  6. william vogel

    william vogel Well-Known Member Gold Supporting Member

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    Where do you get the lacing cord? I’m interested because it’s a wonderful look. I’ll have to figure out how to tie it though. What’s the trick?
     
  7. David Copeland

    David Copeland Member

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    I found it on eBay. There are quite a few folks on there selling it. As for the how-to Google it; there are multiple websites describing how to do it. The metal grills on the cab were from eBay as well. It turns out there are quite a few sellers of this aluminum mesh for car/truck custom grill work. Being aluminum it's fairly easy to shape it to bend toward the outside of the cab for a neat look.
     
  8. william vogel

    william vogel Well-Known Member Gold Supporting Member

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    Here’s a DR103 I built for a guy in Texas earlier this year.
     
  9. David Copeland

    David Copeland Member

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    Very nice! I just went with the ZoSo caps instead of the really expensive ones. But I do have a question; how do you get the wire that strait with the nice 90 degree bends??
     
  10. william vogel

    william vogel Well-Known Member Gold Supporting Member

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    I use topcoat pretinned wire and grip it with needle nosed pliers and make the bends.
     
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  11. David Copeland

    David Copeland Member

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    I should mention, on the lacing, there are a couple of different looks. The first being the NASA method; which is a clove hitch with a square knot tied on top of that. These are discrete ties repeated every so often along the wire bundle. The second method is the "loop stitch" which is faster and looks better IMO. That starts with the NASA clove hitch/square knot but moves along with these running loops. At the end I use a number of loops right up next to each other with a NASA tie on top of them with a separate piece of cord to secure everything. I also find working with a large set of tweezers is useful.
     
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  12. adew1

    adew1 Active Member

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  13. David Copeland

    David Copeland Member

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    It's hard to describe actually, on all settings it's articulate and very touch sensitive. The top end is very much there without being harsh or buzzy; as is the bottom end without being muddy. I'm running it through a JBL 15" or an EV SRO 15" (the original version with the white plastic magnet cover.) Cranked with the channels coupled it takes on a different flavor that's sort of mid range centered but with everything else still there. Oh and the tone stack is very very useful.

    Here's a video that gives an idea, although the pick attacks don't come through on it like live through 15" speakers do.

    And of course, it's LOUD!

     
  14. David Copeland

    David Copeland Member

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    Here's one more Hiwatt demo that makes for some interesting listening. The two of them probably do a better job of describing the Hiwatt sound than I do. The only difference between the DR504 and the DR103 is how deep a hole you can drill in the wall (or anyone's head ) standing in front of the speaker cab.

     

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